Three blocks are in contact with each other

on a frictionless horizontal surface. A 417 N
horizontal force is applied to the block with
mass of 3.7 kg as shown in the figure below.
The acceleration of gravity is 9.8 m/s^2.
(the picture looks like this)
F
*----->[3.7 kg][5.1 kg][7 kg]
What is the net force on the block with
mass 3.7 kg?
Answer in units of N